A stenosed site or an occluded site generated in a vessel of a living body may be treated by expanding the stenosed site or the occluded site using a stent to secure the body vessel. The stent is delivered to a target site (e.g., the stenosed or occluded site), and the stent is then expanded and detained at the target site. For example, International Patent Application Publication No. 2002/028319 discusses a technique in which the stent is expanded by a balloon and is detained at the target site after the stent is delivered to the target site.
When a coat layer such as a drug layer is formed on a surface of the stent (e.g., the outer surface of the stent), the stent and the inner wall of the body vessel of the living body may interfere with each other (e.g., contact one another) while the stent is being delivered to the target site. This contact may damage the coat layer of the stent. Therefore, it is desirable to protect the stent. As an example of the stent protection means, the stent may be covered by a cover.
In this case, the stent is delivered to a target site of the living body while the stent is covered by the cover. Then, the stent is expanded along with the balloon (e.g., the balloon expands or dilates radially outward and the stent correspondingly expands or dilates radially outward so that the outer diameter of the stent increases). When the stent is expanding, the cover is moved to a position separated from the balloon and the stent (e.g., spaced apart from the balloon in the axial direction of the device) in order to prevent inference with the expanding stent. After the stent is detained (i.e., indwelled or held in position at the target site of the body lumen), the balloon is deflated, and the cover is retracted to its original position to cover the balloon (i.e., cover the outer surface of the balloon).